Relational Discrimination Learning Using Multiple Stimulus Pairs with Different Colors and Color Regions in Pigeons

This study investigated whether pigeons could acquire both transitive inference-like responses based on color and transpositions response based on area, through differentiated reinforcement of the relational discriminative response based on the area using stimulus pairs with different color areas and colors. Pigeons were trained to discriminate between stimuli with larger or smaller color areas using six pairs of stimuli with different colors and color areas. Three tests were conducted. In Test 1, a novel combination of the stimuli used in the training was presented as a test pair, and in Test 2 and Test 3, stimulus pairs with the same color or area combination as in Test 1, differing only in color or color area, were presented. In general, the birds elicited similar discriminative responses to the novel stimulus pairs as the training pairs in Test 1. In Test 2, transitive inference-like responses based on color were observed in the birds trained to reinforce responses to larger color area stimuli, and in Test 3, transposition responses were observed in the birds trained to reinforce responses to smaller color area stimuli. These results suggest that through the differential reinforcement of relative discriminative responses using ordinal compound stimulus list, either a transitive inference-like response based on color or a transposition response based on the area is acquired. The results also imply that response acquisition depends on the responses reinforced during training, although the effect of the order in which each training pair was trained should also be considered.